Analyzing the microstructures of W-ZrC composites fabricated through reaction sintering and determining their fracture toughness values by using the SENB and VIF methods

In this research, the mechanical properties, especially the fracture toughness (KIC), and the microstructure of W-ZrC composites made by mixing tungsten carbide (WC) and zirconia (ZrO2) powders and applying the reaction sintering method have been investigated. For this purpose, WC and ZrO2 powders with respective volume proportions of 3:1 and 2:1 were mixed in a planetary mill and formed by a press. After pyrolysis at temperature 650 °C, the specimens underwent reaction sintering in vacuum at temperatures 2150 and 2250 °C. For measuring properties such as hardness, Young's modulus and KIC, two different methods were used and their results were compared with each other. The XRD patterns showed the formation of W-ZrC composite following the sintering process; although slight quantities of W2C and unreacted primary compounds were also observed in each sample. The maximum values of relative density, Young's modulus and KIC (%98.34, 256 GPa and 6.69 MPa·√m, respectively) were obtained in the sample made with WC and ZrO2 powders at respective volume proportions of 3:1 and sintered at temperature 2250 °C. Also, the maximum hardness (9.8 GPa) was obtained in the specimen made with WC:ZrO2 powders at volume proportions of 2:1 and sintered at 2250 °C. By observing the amount of Vickers diamond loading in each case, the maximum difference between the KIC values obtained by a large number of equations in the Vickers Indentation Fracture (VIF) method is less than 8%, and the maximum error between the KIC values obtained by each equation and by the Single-Edge Notch Beam (SENB) method is less than 10% in all the samples.